Scroll type compressor having curved surface portions between the shaft and bearing means

ABSTRACT

A scroll type compressor comprising: a crankshaft having an eccentric shaft portion formed thereon; an orbiting scroll which is given torque by the crankshaft through the eccentric shaft portion; and bearing means for rotatably supporting the crankshaft; wherein at least one of the eccentric shaft portion and the bearing means is constituted by a rotatably engaged bushing and a curved surface portion.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll type compressor, and moreparticularly to a scroll type compressor which is utilized inrefrigeration and air conditioning systems.

A conventional scroll type compressor, which has been disclosed in e.g.Japanese Unexamined Patent Publication No. 80088/1988, is constructed asshown in FIG. 17. In FIG. 17, reference numeral 1 designates a fixedscroll. Reference numeral 2 designates an orbiting scroll. Referencenumeral 3 designates a crankshaft. Reference numeral 4 designates adriving bushing which is rotatably mounted in a bearing part 2a formedin the orbiting scroll 2. Reference numeral 5 designates an Oldham'sring. Reference numeral 6 designates a main frame. Reference numeral 6adesignates a main bearing which is formed in the main frame 6. Referencenumeral 7 designates an electric motor stator. Reference numeral 8designates an electric motor rotor. Reference numeral 9 designates a subframe. Reference numeral 9a designates a sub bearing which is formed inthe sub frame 9. Reference numeral 10 designates a hermetic shell.Reference numeral 11 designates an intake tube which directs arefrigerant from outside. Reference numeral 12 designates a dischargetube. Reference numeral 13 designates a lubricating oil which is storedin a bottom part of the hermetic shell. The crankshaft 3 has aneccentric shaft portion 3a formed at an upper portion. The eccentricshaft portion 3a is fitted into the bearing part 2a through the drivingbushing 4, the bearing part 2a being formed on a base plate undersurfaceof the orbiting scroll 2. The crankshaft 3 has a main shaft portion 3band a sub frame shaft portion 3c formed on its upper end and lower end,respectively, so that the main shaft portion 3b is supported by the mainbearing 6a of the main frame 6 and the sub shaft part 3c is supported bythe sub bearing 9a of the sub frame 9. Reference numerals 14 and 15designate an upper balance weight and a lower balance weight,respectively, which are attached on the opposite sides (in the verticaldirection) of the electric motor rotor 8.

Now, the operation of the conventional scroll type compressor of FIG. 17will be explained. Torque which is generated by the electric motor istransmitted by the crankshaft 3 which is shrinkage fitted into the rotor8. The torque is further transmitted to the orbiting scroll 2 throughthe eccentric shaft portion 3a and the driving bushing 4. The Oldham'sring 5 which works as a rotation preventing mechanism causes theorbiting scroll 2 to carry out such a revolution movement that theorbiting scroll moves along a circular orbit. The revolution movementchanges the volume of a compression chamber formed between the fixedscroll 1 and the orbiting scroll 2 to compress the refrigerant.

The refrigerant enters the hermetic shell 10 from an outer refrigerationcycle through the intake tube 11. The refrigerant is compressed in thecompression chamber to have a high pressure, and then flows out in theouter refrigeration cycle through the discharge tube 12. By the way, athrust direction force of compressive loads of the refrigerant which areapplied to the orbiting scroll 2 is supported by a thrust bearingsurface 6b on an upper end surface of the main frame 6. On the otherhand, a radial direction force F_(g) of the compressive loads istransmitted to the crankshaft 3 through the driving bushing 4 as shownin FIG. 18 . The crankshaft 3 is supported by the main bearing 6a formedin a lower boss of the main frame 6, and by the sub bearing 9a formed inthe sub frame 9.

The upper balance weight 14 and the lower balance weight 15 which aremounted on the opposite ends of the rotor 8 are arranged to be balancedagainst a centrifugal force F_(c1) which is generated by the revolutionmovement of the orbiting scroll 2. Centrifugal forces F_(c2) and F_(c3)which are generated by the upper balance weight 14 and the lower balanceweight 15 are also supported by the main bearing 6a and the sub bearing9a. The lubricating oil 13 which is stored in the bottom part of thehermetic shell 10 is fed to sliding parts such as the bearing parts andthe compression chamber by a centrifugal force caused by the rotation ofthe crankshaft 3.

In the conventional scroll type compressor, the radial direction forceF₉ which is applied to the orbiting scroll in the compression stroke isexerted on the eccentric shaft portion 3a which is at the upper end ofthe crankshaft 3, as explained. However, because the eccentric shaftportion 3a as the exerting point projects from the main bearing 6a ofthe main frame 6 in the direction remote from the bearing 9a, thecompressive load F_(g) causes the crankshaft 3 to be flexture-deformedas shown in FIG. 19. When the crankshaft 3 is flexure-deformed, theeccentric shaft portion 3a is inclined in the bearing part 2a of theorbiting scroll 2, the main shaft portion 3b is inclined in the mainbearing 6a of the main frame 6, or the sub shaft part 3c is inclined inthe sub bearing 9a of the sub frame 9. This creates e.g. a problem inthat load carrying capacities of the respective bearing parts candeteriorate to wear or seize the bearing parts.

In particular, recently, the application of a variable speed operationto a compressor under an inverter control is accompanied by extension ofthe operating range of the compressor from a low speed to a high speedin e.g. air conditioning systems. In a low speed operating area, an oilfilm is difficult to be formed in the bearings. In a high speedoperating area, the centrifugal forces F_(c1), F_(c2) and F_(c3) whichare generated by the orbiting scroll 2, the upper balance weight 14 andthe lower balance weight 15 are increased to further enlarge theflexture-deformation of the crankshaft 3, making the problem morenoticeable, which is demanded to be solved.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the problem, and toprovide a ,highly reliable scroll type compressor capable of preventinga bearing part from being damaged due to wear, seize or the like even ifa crankshaft is flexture-deformed by a radial direction force incompressive loads which are exerted to an orbiting scroll during acompression stroke.

According to a first aspect of the present invention, there is provideda scroll type compressor comprising a crankshaft having an eccentricshaft portion formed thereon; an orbiting scroll which is given torqueby the crankshaft through the eccentric shaft portion; and bearing meansfor rotatably supporting the crankshaft; wherein at least one of theeccentric shaft portion and the bearing means is constituted by arotatably engaged bushing and a curved surface portion.

According to a second aspect of the present invention, there is provideda scroll type compressor comprising a crankshaft having an eccentricshaft portion formed thereon; an orbiting scroll which is given torqueby the crankshaft through the eccentric shaft portion, the bearing meanscomprising bearing devices which are provided in a main frame and a subframe to support the crankshaft at its main shaft portion and sub shaftportion.

In the second aspect, it is advisable that the scroll type compressorfurther comprises an electric motor rotor arranged at an intermediateposition in an axial direction; and an upper balance weight and a lowerbalance weight placed on the opposite ends of the rotor to be balancedagainst a centrifugal force which is generated by an orbiting movementof the orbiting scroll; wherein in order to prevent partial contact frombringing about due to flexture-deformation of the crankshaft in thebearing devices, at least one of the main shaft portion and the subshaft portion has a central portion provided with a barrel shaped bandportion to present a convex surface in the entire peripheral direction,the band portion has a peripheral portion engaged with the bushingthrough a minute gap, and the bushing is coupled to the crankshaft by apin in terms of a rotational direction.

In the second aspect, it is also advisable that the scroll typecompressor further comprises an electric motor rotor arranged at anintermediate position in an axial direction; and an upper balance weightand a lower balance weight placed on the opposite ends of the rotor tobe balanced against a centrifugal force which is generated by anorbiting movement of the orbiting scroll; wherein in order to preventpartial contact from bringing about due to flexture-deformation of thecrankshaft in the bearing devices, the main shaft portion has a centralportion provided with a barrel shaped band portion to present a convexsurface in at least one of a reactive force direction of a compressiveload generated in a compression chamber formed between the orbitingscroll and the fixed scroll, and a reactive force direction of acentrifugal load generated by a revolution movement of the orbitingscroll and rotary movements of the upper and lower balance weights, andthe main shaft portion is engaged with a cylindrical bushing through aminute gap.

In the first aspect, it is advisable that the scroll type compressorfurther comprises an electric motor rotor arranged at an intermediateposition in an axial direction; and the bushing engaged with theeccentric shaft portion and rotatably mounted in a bearing part of theorbiting scroll; wherein in order to prevent partial contact fromarising due to flexture-deformation of the crankshaft in the bearingpart, two couples of oppositely engaged surface portions are formed onthe eccentric shaft portion and the bushing, one of the couples areconstituted by flat surfaces, either of the oppositely engaged surfaceportions in the other couple is constituted by a curved surface which iscurved along an axial direction, and the other engaged surface portionis constituted by a flat surface.

It is further advisable that the scroll type compressor furthercomprises an upper balance weight and a lower balance weight placed onthe opposite ends of the rotor to be balanced against a centrifugalforce which is generated by an orbiting movement of the orbiting scroll;and the bearing means comprising bearing devices which are provided in amain frame and a sub frame to support the crankshaft at its main shaft-portion and sub shaft portion; wherein in order to prevent partialcontact from bringing about due to flexture-deformation of thecrankshaft in the bearing parts for supporting the main shaft and subshaft portions of the crankshaft, at least one of the main shaft portionand the sub shaft portion has a central portion provided with a barrelshaped band portion to present a convex surface in the entire peripheraldirection, the band portion has a peripheral portion engaged with thebushing through a minute gap.

It is still further advisable that the scroll type compressor comprisesan upper balance weight and a lower balance weight placed on theopposite ends of the rotor to be balanced against a centrifugal forcewhich is generated by an orbiting movement of the orbiting scroll; andthe bearing means comprising bearing devices which are provided in amain frame and a sub frame to support the crankshaft at its main shaftportion and sub shaft portion; wherein in order to prevent partialcontact from bringing about due to flexture-deformation of thecrankshaft in the bearing devices, the main shaft portion has a centralportion provided with a barrel shaped band portion to present a convexsurface in the entire peripheral direction, the band portion has aperipheral portion engaged with the bushing through a minute gap, andthe bushing is coupled to the crankshaft by a pin in terms of arotational direction; and wherein the bearing device for supporting thesu-b shaft portion of the crankshaft is constructed by a rolling bearingto prevent partial contact from bringing about in the bearing device dueto flexture-deformation of the crankshaft.

In the first aspect, it is advisable that the scroll type compressorfurther comprises the bushing engaged with the eccentric shaft portionand rotatable mounted in the orbiting scroll; wherein the eccentricshaft portion has a flat surface formed on a part of its peripheralsurface, and a curved surface formed on a location at the side oppositeto the flat surface to be curved along an axial direction, the bushinghas an inner peripheral surface engageable with the eccentric shaftportion, and the inner peripheral surface has flat surfaces formed onlocations corresponding to the flat surface and the curved surface.

In the first aspect, it is also advisable that the scroll typecompressor further comprises the bushing engaged with the eccentricshaft portion and rotatably mounted in the orbiting scroll; wherein theeccentric shaft portion has two flat surfaces formed on its peripheralsurface at opposite sides with respect to the center thereof, thedriving bushing has an inner peripheral surface engageable with theeccentric shaft portion, the inner peripheral surface has a flat surfaceformed thereon at a location corresponding to one of the eccentric shaftportion flat surfaces and a curved surface formed thereon at a locationcorresponding to the other eccentric shaft portion flat surface, thecurved surface being curved along an axial direction.

In the first aspect, it is further advisable that the scroll typecompressor further comprises the bushing engaged with the eccentricshaft portion and rotatably mounted in the orbiting scroll; wherein theeccentric shaft portion has a flat surface formed on a part of itsperipheral surface, and a curved surface formed on a location at theside opposite to the flat surface to be curved along an axial direction,the bushing has an inner peripheral surface engageable with theeccentric shaft portion, and the inner peripheral surface has a curvedsurface formed thereon at a location corresponding to the eccentricshaft portion curved surface and a flat surface formed thereon at alocation corresponding to the eccentric shaft portion flat surface.

In the scroll type compressor according to the present invention, aradial direction force is exerted on the orbiting scroll during acompression stroke, and the force is applied to the eccentric shaftportion which is provided on top of the crankshaft. As a result, thecrankshaft is subject to flexture-deformation. In accordance with thepresent invention, the scroll type compressor is provided with suchbearing means that the eccentric shaft portion, the main shaft portionor the sub shaft portion of the crankshaft has a curved surface, or hasa central portion provided with a barrel shaped band portion to presenta convex surface in the entire peripheral direction. The curved surfaceor the band portion allows a driving bushing or a cylindrical bushing tobe in touch with the curved surface or the barrel shaped surface so asto be axially rotatable and movable. Such an arrangement can drive thecrankshaft in a parallel state with respect to each bearing. As aresult, partial contact can be prevented from bringing about in eachbearing, thereby avoiding occurrence of wear and seize. In addition, abearing load capacity can be prevented from deteriorating, providing ahighly reliable scroll type compressor capable of preventing a bearingfrom being damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a first embodiment of ascroll type compressor according to the present invention;

FIG. 2 is a top plan view showing an eccentric shaft portion on top of acrankshaft in the scroll type compressor of FIG. 1, the eccentric shaftportion having a driving bushing fitted thereon;

FIG. 3 is a sectional view taken along the line III--III of FIG. 2wherein the driving bushing which is fitted thereon in the embodiment ofFIG. 2 is mounted in a bearing part of an orbiting scroll;

FIG. 4 is a cross sectional view showing a state wherein the crankshaftis inclined in a bearing structure of the crankshaft eccentric shaftportion according to the embodiment of FIG. 3;

FIG. 5 is a perspective view showing another structure of the bearingfor the crankshaft eccentric shaft portion;

FIG. 6 is a perspective view showing another structure of the bearingfor the crankshaft eccentric shaft portion;

FIG. 7 is a cross sectional view showing another structure of thebearing for the crankshaft eccentric shaft portion;

FIG. 8 is a cross sectional view showing another bearing structure ofthe crankshaft eccentric shaft portion;

FIG. 9 is a cross sectional view showing a bearing structure forsupporting a main shaft portion of the crankshaft in accordance with asecond embodiment of the scroll type compressor;

FIG. 10 is a cross sectional view showing another structure of thebearing for the crankshaft main shaft portion;

FIG. 11 is an exploded and perspective view showing another structure ofthe bearing for the crankshaft main shaft portion;

FIG. 12 is a cross sectional view showing a bearing structure forsupporting the crankshaft sub bearing portion in accordance with anotherembodiment of the scroll type compressor;

FIG. 13 is a cross sectional view schematically showing a state whereinthe crankshaft is inclined in the bearing structure of the crankshaftsub shaft part of FIG. 12;

FIG. 14 is a cross sectional view showing another structure of thebearing for the crankshaft sub shaft portion;

FIG. 15 is a cross sectional view showing another structure of thebearing for the crankshaft sub shaft portion;

FIG. 16 is a cross sectional view schematically showing a state whereinthe crankshaft is inclined in the bearing structure of the crankshaftsub shaft portion of FIG. 15;

FIG. 17 is a longitudinal sectional view showing a conventional scrolltype compressor;

FIG. 18 is a schematic view showing the directions of compressive loadsand centrifugal forces of balance weights which are exerted on acrankshaft in the conventional scroll type compressor; and

FIG. 19 is a schematic view showing how the crankshaft is inclined inthe conventional scroll type compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The scroll type compressor according to the present invention will bedescribed in detail, referring to embodiments shown in the accompanyingdrawings. In FIG. 1, there is shown the scroll type compressor 20according to a first embodiment of the present invention. In FIG. 1showing the scroll type compressor 20 of the first embodiment, similaror corresponding parts are indicated by the same reference numerals asthe conventional scroll type compressor shown in FIG. 17, andexplanation of those parts will be omitted for the sake of simplicity.

The scroll type compressor 20 of the embodiment includes a crankshaft 21which has an electric motor rotor 8 fixed by shrinkage fit at anintermediate portion thereof in its axial direction. The crankshaft 21has an upper portion formed integrally with an eccentric shaft portion22 which is fitted into a bearing part 2a of an orbiting scroll 2 togive torque directly to the orbiting scroll 2. The crankshaft has a mainshaft portion 23 formed thereon at a lower position than the eccentricshaft portion and a sub shaft portion 24 formed thereon at a lower end,the main shaft portion 23 being supported by a main shaft bearing 6a ofa main frame 6, and the sub shaft portion 24 being supported by a subbearing 9a of a sub frame 9. Bearing devices, i.e. bearing structuresfor supporting the eccentric shaft portion 22, the main shaft portion 23and the sub shaft portion 24 formed on the crankshaft 21 will beexplained one after another.

In FIGS. 2 and 3, there are shown cross sectional views whichschematically show a bearing structure of the eccentric shaft portion 22formed on the upper end of the crankshaft 21 in the scroll typecompressor 20 in accordance with the first embodiment. As can be clearlyseen in FIG. 2, the eccentric shaft portion 22 has an external shapethat is formed to be based on a circle whose center O₂ lies at alocation shifted by a predetermined length with respect to the center O₁of the crankshaft 21. When the line connecting the two centers O₁ and O₂is defined as Y--Y, and a line perpendicular to the line Y--Y is definedas X--X, the eccentric shaft portion 22 has a flat surface 22a formed ona peripheral surface thereof in the direction along the line Y--Y. Theeccentric shaft portion 22 also has a curved surface 22b formed on theperipheral surface at the side opposite the flat surface 22a, the curvedsurface 22b presenting a convex surface outwardly along an axialdirection.

On the other hand, the eccentric shaft portion 22 has a driving bushing25 engaged thereon in such a manner that the driving bushing 25 isrotatably mounted in the bearing part 2a of the orbiting scroll 2. Thedriving bushing 25 has a bore formed therein to be engageable with theeccentric shaft portion 22. The inner peripheral surface of the bore isformed with flat surfaces 25a and 25b at locations which correspond tothe flat surface 22a and the curved surface 22b of the eccentric shaftportion 22, respectively. The eccentric shaft portion 22 is put into thebore of the driving bushing 25 with a predetermined gap therebetween asshown in FIG. 3. Even if the eccentric shaft portion 22 is as shown inFIG. 4 when the eccentric shaft portion 22 having such a structurecauses the orbiting scroll 2 to carry out an orbiting movement throughthe driving bushing 25, the driving bushing 25 can rotate with aparallel position to the bearing in the bearing part 2a of the orbitingscroll 2, without being inclined with the eccentric shaft portion 22.This is because the curved surface 22b is in touch with thecorresponding flat surface 25b of the driving bushing 25 to be rotatableand movable in the axial direction. This arrangement can eliminatepartial contact from occurring in the bearing part 2a of the orbitingscroll 2, prevent bearing performance from deteriorating, decrease wearand be free from seizure.

Referring now to FIG. 5, there is shown a perspective view of anotherembodiment of the eccentric shaft portion which is formed on the top endof the crankshaft 21. In this embodiment, the eccentric shaft portion isindicated by reference numeral 26. The eccentric shaft portion 26 isbasically similar to the eccentric shaft portion 22 shown in FIG. 2. Theeccentric shaft portion 26 has an outer shape which is formed based on acircle with the center O₂. The center O₂ is shifted at a predetermineddistance from the center O₁ of the crankshaft 21. The eccentric shaftportion 26 includes an eccentric pin 21a which has a flat surface 26aformed on a peripheral surface at a location which extends along theline connecting between the two centers O₁ and O₂. The eccentric pin 21ahas the peripheral surface formed with a cutout 26b on the side oppositethe flat surface 26a, the cutout being U-shaped as viewed from the top.

Into the cutout 26b is inserted a separate coupling member 27 fromupward, the coupling member having a front end formed with a curvedsurface 27a and a rear end formed with a flat surface 27b as clearlyshown in FIG. 5. The coupling member 27 has such a shape which isobtained by cutting off a part of the peripheral portion of acylindrical body in its longitudinal direction. The coupling member 27is mounted into the cutout 26b of the eccentric shaft portion 26 in sucha manner that the curved surface 27a projects to be convex in an outwarddirection along the axial direction of the eccentric shaft portion 26.By this arrangement, the eccentric shaft portion 26 can have asubstantially same structure as the eccentric shaft portion 22 shown inFIG. 2. A driving bushing which is identical to the one shown in FIG. 2can be used to be engaged with the eccentric shaft portion 26, andexplanation of the driving bushing for the eccentric shaft portion 26will be omitted for the sake of simplicity.

Referring now to FIG. 6, there is shown another embodiment of thedriving bushing which is mounted onto the eccentric shaft portion formedon the top of the crankshaft 21. The driving bushing of this embodimentis indicated by reference numeral 28. The driving bushing 28 has a bore28a formed therein to be basically engageable with the basic circle ofthe eccentric shaft portion like the driving bushing 25 shown in FIG. 2.The bore 28a has a flat surface 28b and a cutout 28c formed on an innerperipheral surface thereof in such a manner that the flat surface 28b isperpendicular to a diametrical center line of the bore and the cutout28c is opposite to the flat surface 28b. Into the cutout 28c is inserteda separate coupling member whose shape is identical to the couplingmember 27 shown in FIG. 5. The coupling member 27 is mounted in such amanner that the curved surface 27a projects to be convex in an inwarddirection with respect to the axial direction of the driving bushing 28.When the driving bushing 28 is used, the eccentric shaft portion whichhas the driving bushing 28 engaged with and mounted to it is differentfrom the eccentric shaft portion shown in FIG. 2 in that the outerperipheral surface on the side opposite one of the flat surfaces 22a isnot curved but a flat surface. It means that the eccentric shaft portionand the driving bushing have such a relation that two couples ofoppositely engaged portions are formed on the opposite peripheralsurfaces (the outer peripheral surface of the eccentric shaft portionand the inner peripheral surface of the driving bushing) at locationsalong the line connecting between the center O₁ of the crankshaft andthe center O₂ of the eccentric shaft portion, that one of the couples isconstituted by flat surfaces (e.g. the flat surfaces 22a and 25a asshown in FIG. 2), and that either of the oppositely engaged surfaceportions in the other couple is constituted by a curved surface asstated above, and the other engaged surface portion is constituted by aflat surface.

When the separate coupling member 27 is prepared and is mounted into thecutout formed in the eccentric shaft portion or the driving bushing asshown in FIGS. 5 and 6, it is possible to eliminate difficulty which isinvolved by working in a direct and precise manner the curved surfacewhich curves in a direction along the axis of the eccentric shaftportion outer peripheral surface of the crankshaft. It is also possibleto eliminate similar difficulty with respect to the inner peripheralsurface of the engaged bore of the driving bushing. In addition, such asolution can not only improve processability and processing precisionbut also decrease a processing cost. The concept of the curved surfacewhich is formed on either of the one couple of oppositely engagedsurface portions between the eccentric shaft portion and the drivingbushing includes such an arrangement that the eccentric shaft portionhas a groove 29 formed therein to be perpendicular to the axialdirection thereof, and the groove 29 has a cylindrical roller 30inserted therein.

In the case of FIG. 7, the cylindrical roller 30 which is a generalpurpose part can be used to remarkably improve processability, therebyallowing a processing cost to be lowered. As shown in FIG. 8, the othercouple of oppositely engaged surface portions can have a highly hardmember 31 such as a hardened steel arranged between the curved surface(e.g. the curved surface 22b of the eccentric shaft portion 22) and thecorresponding flat portion (e.g. the flat surface 25b of the drivingbushing 25) to ensure enough hardness on both contact portions. In thiscase, the driving bushing can be made from a material having relativelylower hardness, such as a sintered material. Such an arrangement canoffer an advantage in that reliability is ensured while a processingcost is decreased.

Referring now to FIG. 9, there is shown a bearing structure whichsupports the main shaft portion 23 of the crankshaft 21 at the mainbearing part 6a of the main frame 6 in the scroll type compressor 20.The main shaft portion 23 has a central portion provided with a barrelshaped band portion 32 to present a convex surface in the entireperipheral direction. The maximum projected portion which lies at thecentral portion of the barrel portion 32 has a cylindrical bushing 33engaged on the periphery thereof with a minute gap. The cylindricalbushing 33 is seated on a seat surface 21a which is formed at a lowerportion of the main shaft portion of the crankshaft 21.

The cylindrical bushing 33 is rotatably within the main bearing part 6aof the main frame 6, and rotates together with the crankshaft 21. Toaccomplish this, a bottom surface 33a of the cylindrical bushing and theseat surface 21a are formed with holes in the axial direction, and aconnecting pin 34 is press fit into each of the holes. This arrangementallows the cylindrical bushing 33 to rotate together with the crankshaft21. Either of the holes which the connecting pin 34 is press fit into isformed as an elongated hole which is elongated in a radial directionbecause the crankshaft 21 is inclined with respect to the cylindricalbushing 33 when the crankshaft 21 receives a compressive load F_(g).Although in the case of FIG. 9 the hole which is formed in the sheetsurface 21a is elongated, the hole which is formed in the bottom surface33a of the cylindrical bushing 33 may be elongated.

In accordance with the bearing structure which is constituted by themain shaft portion 23 of the crankshaft 21 having the central portionprovided with the barrel shaped band portion to present the convexsurface in the entire peripheral direction, and the cylindrical bushing33 arranged in the main bearing part 6a of the main frame 6, thecontacting points between the curved surface on the band portion 32 ofthe main shaft portion 23 and the cylindrical bushing 33 can movefollowing a flexing direction and a flexing magnitude of the crankshaft21 though the compressive load F_(g) and centrifugal loads F_(c1),F_(c2) and F_(c3) which are applied on the crankshaft 21 aresubstantially rectangular in their directions, and their magnitudes varydepending on the operating conditions of the compressor to change theflexing direction of the crankshaft 21. Irrespectively of the operatingconditions of the compressor, the cylindrical bushing 33 can rotatewhile constantly maintaining a parallel state to the main bearing part6a of the main frame 6 (maintaining such a state that the centralrotating axis of the cylindrical bushing 33 corresponds to the centralaxis of the main bearing part 6a).

Such an arrangement can offer a highly reliable bearing structure whichprevents a bearing load carrying capacity from falling and is free ofwear, seizure or the like in the bearing.

By the way, when the cylindrical bushing 33 has moved its contactingpoint on the curved surface of the band portion on the main shaftportion 23 of the crankshaft 21, a gap is apt to be formed between thesheet surface 21a and the bottom surface 33a of the cylindrical bushing33. However, the gap can be minimized by selecting suitable curvature ofthe curved surface of the band portion 32. In this manner, an oil forlubricating the cylindrical bushing 33 can be prevented from flowing outof the gap.

Although in the bearing structure of the crankshaft main shaft portion23 stated above, the seat surface 21a to the cylindrical bushing 33 isformed on the crankshaft 21, the seat surface may be an upper surface14a of an upper balance weight 14 as shown in FIG. 10. In this case, thecrankshaft 21 can have the outer diameter formed in a size smaller thanthe main shaft portion outer diameter throughout its entire length,thereby improving machinability of the crankshaft.

As shown in FIG. 11, the main shaft portion 23 of the crankshaft 21 maybe formed in such a manner that two surfaces which are located in areactive force direction of the compressive load direction F_(g) and ina reactive force direction of centrifugal loads F_(c1), F_(c2) andF_(c3) (F_(c3) is not shown in FIG. 11 but is understood to be the sameas shown in FIG. 18) have curved surfaces 23a and 23b formed on centralportions thereof to present convex surfaces, that a cylindrical bushing35 which has flat surfaces 35a and 35b formed on the inner peripheralsurface thereof at locations corresponding to the curved surfaces 23aand 23b, and that the main shaft portion 23 has the cylindrical bushing35 engaged therewith. Such an arrangement allows the cylindrical bushing35 to follow flexure-deformation of the crankshaft 21 due to thecompressive load F_(g), and the centrifugal loads F_(c1), F_(c2) andF_(c3), and to move its contacting points on the curved surfaces 23 aand 23b of the main shaft portion 23 of the crankshaft 21. As a result,the cylindrical bushing can be rotated, maintaining a parallel state tothe main bearing part 6a of the main frame 6, and can offer an advantagesimilar to the bearing structure stated above. In this case, the twocurved surfaces 23a and 23b can also work to connect the crankshaft 21and the cylindrical bushing 35 in a circumferential direction to need noconnecting pin.

Referring now to FIG. 12, there is shown a bearing structure whichsupports the crankshaft 21 by a sub bearing part 9a in a sub frame 9 ina scroll type compressor 20. In the bearing structure, a sub shaftportion 24 of the crankshaft 21 has a central portion provided with abarrel shaped band portion 36 to present a convex surface like thebearing structure for supporting the main shaft portion 23 of thecrankshaft 21 in the main bearing part 6a of the main frame 6 statedabove. The bearing structure is constituted by engaging a cylindricalbushing 37 with the sub shaft portion 24 with a minute gap around theouter circumference of the band portion.

In order that the cylindrical bushing 37 can rotate with the crankshaft21 as one unit, a connecting pin 38 has one end press fit into a holeformed in the cylindrical bushing in a radial direction, and has theother end engaged in an elongated hole 24a which is formed in thecrankshaft 21 to be long in the axial direction. In this manner, thecylindrical bushing and the crankshaft are interconnected in thecircumferential direction. In FIGS. 1 and 12, reference numeral 16designates an oil supply pump, and reference numeral 17 designates acover for the oil supply pump.

In accordance with such an bearing structure wherein the sub shaftportion 24 of the crankshaft 21 is supported by the sub bearing part 9ain the sub frame 9, when the crankshaft 21 has flexture-deformationcaused therein as shown in FIG. 13, the contacting points between thesub shaft portion 24 of the crankshaft 21 and the cylindrical bushing 37arranged around the outer circumference of the sub shaft portion 24moves on the barrel shaped band portion which presents the convexsurface in the central portion of the sub shaft portion 24. As a result,the cylindrical bushing 37 can rotate while maintaining a parallel stateto a boss of the sub frame 9, i.e. the sub bearing part 9a. Such anarrangement can prevent a bearing load carrying capacity from lowering,and offer a highly reliable bearing structure which is free from wear,seizure or the like in the bearing.

Although in the bearing structure for supporting the sub shaft portion24 of the crankshaft 21 stated above, the sub shaft portion 24 of thecrankshaft 21 has the central portion provided with the barrel shapedband portion 36 to present the convex surface, and the cylindricalbushing 37 is engaged on the outer circumference of the band portion 36,the bearing structure may be constituted by a cylindrical bushing 39whose inner peripheral surface has a central portion provided with abarrel shaped band portion 39a to present a convex surface, and which isengaged with the crankshaft 21 as shown in FIG. 14.

Although the connecting pin 38 which have the one end press fit into thehole in the cylindrical bushing 37 is engaged in the elongated hole 24aformed in the crankshaft 21 to offer a connecting mechanism for thecrankshaft 21 and the cylindrical bushing 37 in their rotary directionin the embodiment described earlier, such an arrangement wherein anelongated hole is formed in the cylindrical bushing 39, a hole is formedin the sub shaft portion 24 of the crankshaft 21, and the connecting pin38 has one end press fit into the hole in the sub shaft portion 24 andthe other end engaged in the elongated hole may be adopted.

Although in the bearing structure for supporting the sub shaft portion24 of the crankshaft 21 as stated earlier, the sub shaft portion 24 orthe cylindrical bushing 39 has the central portion provided with thebarrel shaped band portion to present the convex surface, the sub shaftportion 24 of the crankshaft 21 may be supported by the sub bearing part9a by use of a rolling bearing as shown in FIG. 15 because a compressiveload and a centrifugal load which are applied on the sub bearing part 9aof the sub frame 9 are generally smaller than those applied to theeccentric shaft portion 22 and the main shaft portion 23. When therolling bearing 40 (deep groove ball bearing in FIG. 15) is used, aninner ring 40a is mounted to the crankshaft 21 by clearance fit becausethe scroll type compressor is subjected to a load fixed to an inner ring(a load direction rotates, the inner ring rotates and an outer ring isstandstill).

When a load is applied to the crankshaft 21 in a bearing structure forsupporting the shaft portion 24 of the crankshaft 21 by means of therolling bearing 40, the inner ring 40a is inclined with respect to aload direction as shown in FIG. 16 to follow the inclination of thecrankshaft 21. The inclination of the crankshaft 21 does not damage aload carrying capacity or reliability of the rolling bearing 40. Even ifthe crankshaft 21 is inclined, a load carrying capacity or reliabilityof the bearing is prevented from lowering.

Although in the scroll type compressor according to the embodiment shownin FIG. 1, the bearing structure for supporting the eccentric shaftportion 22, the main shaft portion 23 and the sub shaft portion 24 ofthe crankshaft 21 are constituted by arranging the driving bushing 25 orthe cylindrical bushing 33 or 37, and forming the bearing surfaces ofthe respective shaft portions in such convex curved surfaces that therespective bearing surfaces work as parallel bearings to the respectivebushing, at least one of the eccentric shaft portion, the main shaftportion and the shaft portion of the crankshaft 21 can be supported bythe bearing structure stated above to prevent a bearing load carryingcapacity in the shaft portion from lowering.

We claim:
 1. A scroll type compressor comprising:a rotatable crankshafthaving an eccentric shaft portion formed thereon; a fixed scroll; anorbiting scroll cooperable with said fixed scroll to compress gas; andbearing means rotatably connecting said orbiting scroll to saideccentric shaft portion so as to orbitally drive said orbiting scroll,wherein said bearing means comprises: a) a bushing having an outerperiphery fitted in said orbiting scroll, and b) a non-rotatableconnection between said bushing and said eccentric shaft portion, saidnon-rotatable connection including a portion curved in the direction ofthe axis of rotation of the crankshaft.
 2. The scroll type compressor ofclaim 1 wherein said non-rotatable connection further comprisescooperating flat surfaces on said bushing and said eccentric shaftportion.
 3. A scroll type compressor according to claim 2, furthercomprising:an upper balance weight and a lower balance weight placed onthe opposite ends of the rotor to be balanced against a centrifugalforce which is generated by an orbiting movement of the orbiting scroll;and a rotor coupled to said crankshaft for driving said crankshaft; thebearing means comprising bearing devices which are provided in a mainframe and a sub frame to support the crankshaft at its main shaftportion and sub shaft portion via further bushings; wherein in order toprevent partial contact from occurring due to flexture-deformation ofthe crankshaft in the bearing parts for supporting the main shaft andsub shaft portions of the crankshaft, at least one of the main shaftportion and the sub shaft portion has a central portion provided with abarrel shaped band portion to present a convex surface in the entireperipheral direction, the band portion has a peripheral portion engagedwith the further bushings through a minute gap.
 4. A scroll typecompressor according to claim 2, further comprising:an upper balanceweight and a lower balance weight placed on the opposite ends of therotor to be balanced against a centrifugal force which is generated byan orbiting movement of the orbiting scroll; and the bearing meanscomprising bearing devices which are provided in a main frame and a subframe to support the crankshaft at its main shaft portion and sub shaftportion via further bushings; wherein in order to prevent partialcontact from occurring due to flexture-deformation of the crankshaft inthe bearing devices, the main shaft portion has a central portionprovided with a barrel shaped band portion to present a convex surfacein the entire peripheral direction, the band portion has a peripheralportion engaged with the further bushing through a minute gap, and thefurther bushing is coupled to the crankshaft by a pin in terms of arotational direction; and wherein the bearing device for supporting thesub shaft portion of the crankshaft is constructed by a rolling bearingto prevent partial contact from occurring in the bearing device due toflexture-deformation of the crankshaft.
 5. A scroll type compressorcomprising:a main frame; a sub frame a crankshaft rotatably mounted insaid main frame and said sub frame via bushings, said crankshaft havingan eccentric shaft portion formed thereon, wherein the main frame andsub frame are mutually spaced along the axis of the crankshaft; a fixedscroll; an orbiting scroll cooperable with the fixed scroll to compressgas, said orbiting scroll being drivingly mounted on said eccentricshaft portion; a electric motor mounted between said main frame and saidsub frame and having a rotor coupled to said crankshaft for driving saidcrankshaft; upper and lower balance weights placed at opposite ends ofsaid rotor for balancing orbiting movement of said orbiting scroll; apin rotatably coupling at least one of the bushings to a respective oneof the main frame and the sub frame; and a circumferentially continuousbarrel shaped band portion presenting a convex surface and formed onsaid crankshaft to engage at least one of the bushings through a minutegap.
 6. A scroll type compressor comprising:a main frame; a sub frame; acrankshaft rotatably mounted in said main frame and said sub frame viabushings, said crankshaft having an eccentric shaft portion formedthereon, wherein the main frame and sub frame are spaced along the axisof the crankshaft; a fixed scroll; an orbiting scroll operable with thefixed scroll to compress gas, said orbiting scroll being drivinglymounted on said eccentric shaft portion; a electric motor mountedbetween said main frame and said sub frame and having a rotor coupled tosaid crankshaft for driving said crankshaft; upper and lower balanceweights placed at opposite ends of said rotor for balancing orbitingmovement of said orbiting scroll; and two couples formed between saidcrankshaft and the bushing of said main frame, each of said couplescomprising a flat surface on one of said crankshaft and said bushing,and a surface curved in the direction of the axis of rotation of thecrankshaft and engaged with said flat surface.